The invention relates to a turning machine having a multiple track bed, a spindle head with a drive device for a work mount, and a rest, preferably designed as a compound slide or machining turret, for mounting tools or driveable machining units.
The turning machines previously comprising a two-track machine bed having a spindle head for work mounting, a tailstock as a counterstay, and also a rest as a tool-holder have now been further developed into high-production turning machines or high-production machining centers. The two-track bed has been further developed into a three-track bed or a four-track bed for independently moving the rest relative to the other parts of the turning machine. In particular, the rest has been extensively developed further as a machining center or a universal tool holder having separate drive devices for tool mounting or complete machining units. Apart from fixed turning tools, driven machining units for grinding, milling and boring are therefore fixed on the rest (DE-A No. 1-34 10 276).
In these known machining centers, the rest, apart from executing the known motion (X.sub.1 -axis) transversely to the longitudinal axis of the machine bed by means of a compound slide on a separate carriage (four-track bed), also executes a separate longitudinal motion (Z-axis) parallel to the longitudinal axis of the machine bed. In addition to this cross motion in a horizontal plane, the rest can execute a motion in a vertical axis (Y-axis) and also a rotary motion about this vertical axis (B-axis). With a numerically controlled drive, turning machines of this type can be used as universal metal-cutting machines.
In these known metal-cutting machines, the spindle head is essentially used for mounting the workpiece, with the spindle executing the rotary motion (C-axis) about the longitudinal axis of the workpiece. In this connection, it is known to carry out the rotary motion of the spindle of the spindle head in preset angular steps.
The known universal turning machines have the disadvantage that on the one hand all possibilities of optimally machining a workpiece are hereby not yet exhausted. On the other hand, it is disadvantageous that the rest assumes spatial motion sequences for which it is not necessarily suitable. If, for example, it is desired to produce a tapered circumference on the workpiece, the rest can only achieve this by moving outward gradually in the transverse direction (X-axis). During this procedure, it is not always guaranteed that the cutting tool is always perpendicular to the cutting surface, i.e. the angle of contact does not correspond to the surface normals.
In the known universal machining centers, it can also be of disadvantage that the rest described, which is of complicated construction, as a machining turret has to be of very elaborate design so that the requisite spatial motion sequences can be executed, not least also in combination with a very complicated numerical control system. Because of the guides for the drive units of the rest, which guides are arranged in the most restricted construction space, the machining accuracy can only be produced by maximum precision of the components, with the rigidity and stability of the system of the rest leaving something to be desired.